Combustion – Process of combustion or burner operation – Flame shaping – or distributing components in combustion zone
Reexamination Certificate
2001-02-22
2003-06-17
Price, Carl D. (Department: 3743)
Combustion
Process of combustion or burner operation
Flame shaping, or distributing components in combustion zone
C431S116000
Reexamination Certificate
active
06579086
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a boiler or water heater equipped with a burner, including a housing surrounding a boiler compartment, a cylindrical heat exchanger, which divides the boiler compartment into a combustion chamber, and an exhaust chamber; whereby said heat exchanger comprises passages distributed across its surface for the hot exhaust gas, and a burner head positioned in the combustion chamber.
2. Review of the Prior Art
Such a boiler or water heater is disclosed in the French Patent document No. 93 00498, and is incorporated herein by reference. It contains a number of boiler designs, which exhibit the above-mentioned design features. These boilers are designed to accommodate gas burners and comprise a cylindrical casing with the sides closed off, and a plurality of flame openings distributed across the surface area. Such a gas-fired boiler or water heater is space-saving in its design and does not require a separate furnace room.
It has been a long-standing desire for such a space-saving furnace to be capable of being operated with fuel oil. The disadvantage of using gas as fuel is the more complex fuel storage requirements as compared to oil. As a result, the gas furnace has to rely on either an expensive pressurized tank or on a connection to a gas distribution network. Oil, on the other hand, has been stored in sufficient quantities in tanks located at the site of the furnace in thousands of installations without any problems. Additionally, the supply and filling of the tanks with oil is substantially simpler and less dangerous as compared to gas.
It is therefore the purpose of the invention to provide a furnace, which can be operated by an oil burner without making it larger than a comparable gas furnace. Furthermore, the furnace should be capable to be operated with a gas or an oil burner. Additionally, it is an objective of this invention to provide a furnace characterized by low exhaust emissions, reduced heat loss, and low noise levels.
SUMMARY OF THE INVENTION
The objectives are met, in accordance to the intent of this invention, by adding a fire tube comprising an axial flame opening and a flame deflection piece positioned at a distance to the flame opening to the burner head; whereby, the fire tube is designed in such as manner that the flame between the fire tube and the heat exchanger is deflected.
One of the advantages of a furnace designed per this invention is that it can be operated by burners, which produce a lance-shaped flame. Such a flame usually requires a very long combustion chamber. A flame deflection piece, designed in accordance to this invention, allows the length of the combustion chamber to be significantly reduced. The deflection piece turns the flame back to its origin and, as a result, reduces the length of the combustion chamber by ½. This allows the combustion chamber to be almost fully saturated by the flame exiting the fire tube which is subsequently being deflected into the opposite direction. The deflection of the flame to its origin has the further advantage that very hot gas is present around the fire tube very soon after the flame is initiated, enhancing the cold start characteristics of the furnace. Another advantage of deflecting the flame in the above-described manner lies in the fact that the combustion chamber can be utilized much more effectively and, therefore, can be designed in a more compact fashion as compared to those systems that produce a long, thin flame. More specifically, because of the burner head being surrounded by the flame, the entire length of the combustion chamber is more thermally uniform and therefore better-suited to exchange heat energy to the heat exchange medium.
It is advisable for the heat exchanger to comprise a blocking plate, which effectively limits the combustion system in lengthwise direction. In addition to the exhaust chamber, this creates an additional chamber into which exhaust gas flows from the exhaust chamber. The exhaust gas is cooled by the heat exchanger and is partially re-circulated back to the fire tube in order to cool the flame, and partially exhausted through the flue. A preferred blocking plate design separates the discharge chamber from the boiler compartment at its side facing away from the combustion chamber, whereby said discharge chamber is connected to the flue. Such a discharge chamber resides axially inside the boiler. This allows a uniform flow of the exhaust gas from peripheral the areas into the discharge chamber. This avoids non-uniform thermal loading issues of the heat exchanger. It is preferred for the blocking plate to separate a re-circulation chamber from the boiler compartment. Cooled exhaust gas can then re-circulate through this re-circulation chamber into the fire tube in order to cool the flame. The re-circulation chamber can also serve the function of a discharge chamber. It would be preferred, if the discharge chamber and/or re-circulation chamber (separated by the blocking plate) were surrounded by the heat exchanger. This allows additional cooling of the exhaust gas entering these chambers prior to leaving the furnace. As a result of the dual contact with the heat exchanger, the exhaust gas is cooled to approximately 80 degrees C., at continuous operation under full load. This allows for the exhaust gas to be piped directly into a flue (made of a plastic compound) upon exiting the boiler.
Further, it would be preferred that the blocking plate between the combustion chamber and the exhaust discharge chamber is shaped in a curved manner in such a way as to allow an increase in the length of the combustion chamber while minimizing the space requirements of the exhaust discharge chamber. Such a design feature results in a relatively large ratio of the heat exchanger surface surrounding the exhaust discharge chamber with respect to its volume.
In order to reduce the number of required parts, the flame deflection piece should form the blocking plate. In doing so, the position of the deflection piece in relation to the housing wall has certain acoustic advantages. The domed surface should point towards the exhaust discharge chamber. The purpose of this domed surface is to deflect the flame without the participation of any heat exchange elements, permitting the use of the entire heat exchange area since the deflection piece does not obstruct any passages for the hot exhaust gas. A preferred flame deflector design comprises a flame separator, positioned along the centerline of the flame and a ring-shaped deflector dish, which surrounds the flame separator. The flame separator divides the flame, and the deflector dish reflects the flame in order to change the flame direction by 180 degrees. The deflector dish should be made circumferentially uniform in order for the flame to retain a uniform shape after its deflection.
The casing of the heat exchanger consists of pipes positioned adjacent to one another with clearance between the pipes; whereby, said pipes are positioned to surround the combustion chamber and are connected to a supply and a return line. The heat exchange pipes should be wound in a screw-like manner. Such a heat exchanger unit is easy to manufacture; it comprises a large surface area and provides for passages between the pipes. Additionally, pipes can be made to thinner wall thicknesses as compared to castings, and therefore offer a more dynamic heat transfer characteristic which is reflected by higher performance at reduced space requirements. It would also be beneficial if this heat exchanger were assembled from a plurality of heat exchanger units. The individual heat exchanger units have the advantage of using shorter pipe lengths, as compared to a single unit having one long pipe system, resulting in higher through-flow velocities.
The heat exchanger units should be connected to the supply and return in parallel. Heat exchanger units using individual elements disclosed in the French Patent No. 93 00498 are applied successfully. The units described in said documents a
Allemann Andreas
Allemann Marco
Boner Heinrich
Fullemann Jorg
Baker & Daniels
Price Carl D.
R.W. Beckett Corporation
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